Research could lead to better-tasting tomatoes, other benefits

Saturday, August 31, 2013 9:00 AM

WEST LAFAYETTE, Ind. — Some compounds that determine plant
species’ characteristics such as the taste of tomatoes can be engineered to
produce larger quantities in plants that have few or none of them, researchers
at Purdue University have found.

Tomatoes available in the Northern states typically are
grown in warmer climates, such as in Florida, California and Mexico, and
harvested immature and still green so that they can ripen during or after
shipment. But picking them before they are ripe affects their flavor, which has
led to complaints from consumers.

“The research ultimately could lead to a variety of uses,
such as in improving the taste of fruits including fresh-market tomatoes, in
increasing the resistance of plants against pests or diseases, or in producing
certain flavors, fragrances and pharmaceuticals,” said Natalia Dudareva,
distinguished professor of biochemistry.

The research involving metabolic engineering also was
conducted by Purdue postdoctoral research associate Michael Gutensohn, with
collaborators at the University of Michigan and in Israel. It was published in
the August edition of The Plant
Journalas the cover story.

Terpenes, a class of volatile compounds, are important
because they often determine how fruits taste; how the flowers of a plant smell,
thus attracting pollinators; and what characteristics plants might have to repel
or defend themselves against pests.

The goal in the research was to determine how metabolic
engineering can be used to produce large quantities of monoterpenes, a
particular group of terpenes, to improve taste and aromatic qualities of
fruits.

The researchers at Purdue used tomato fruits for their
metabolic engineering studies to increase production of monoterpenes. Tomatoes
are an ideal system for this research because during ripening they accumulate
large amounts of carotenoids, the red pigment giving these fruits their
characteristic color.

Carotenoids and terpenes are made from the same molecular
building blocks, which allowed the researchers to tap into the pool of building
blocks naturally available in tomato fruits and then engineer the production of
monoterpenes.

The researchers learned that the largest quantities of
monoterpenes were obtained through the combination of two enzymatic steps.

In the first step, two of the available molecular building
blocks are fused together to build an intermediate product. In the second step,
the chemical structure of this intermediate is further modified, leading to the
formation of monoterpenes.

The research was funded by grants from the Agricultural and
Food Research Initiative of the U.S. Department of Agriculture and the United
States-Israel Binational Agricultural Research and Development Fund.